1. L.J Institute Of Engineering And Technology Iron Carbon Diagram Subject in charge :Mr Sudeep Kolhar/Mr. Dhruv Patel
Sr .No
Student Name
Enrolment no
Suject 1
Mohit Adesara
Definition of structures 2
Bhaavan Dave
Introduction 3
Pragnesh Katakpara
Explanation of iron carbon diagram 4
Faizan Ghasura
Austenite -Ferrite transformation

2. Content Introduction Iron Carbon diagram Definition of structures
Explanation of iron carbon diagram
The Austenite to ferrite / cementite transformation

3. IRON IRON-CARBON DIAGRAM
Eutectic
eutectoid
Pearlite and Cementine
Austenite
Ferrite
Pearlite
Pearlite and
Carbide
Steel
Cast iron

4. Definition of structures
Various phases that appear on the Iron-Carbon equilibrium phase diagram are as under:
Austenite
Ferrite
Pearlite
Cementite
Martensite*
Ledeburite

5. Unit Cells of Various Metals
FIGURE - The unit cell for (a) austentite, (b) ferrite, and (c) martensite. The effect of the percentage of carbon (by weight) on the lattice dimensions for martensite is shown in (d). Note the interstitial position of the carbon atoms and the increase in dimension c with increasing carbon content. Thus, the unit cell of martensite is in the shape of a rectangular prism.

6. Microstructure of different phases of steel

7. Definition of structures
Ferrite is known as α solid solution.
It is an interstitial solid solution of a small amount of carbon dissolved in α (BCC) iron.
stable form of iron below 912 deg.C
The maximum solubility is % C at 723C and it dissolves only % C at room temperature.
It is the softest structure that appears on the diagram.

8. Definition of structures
Ferrite
Average properties are:
Tensile strength = 40,000 psi;
Elongation = 40 % in 2 in;
Hardness > Rockwell C 0 or > Rockwell B 90

9. Definition of structures
Pearlite is the eutectoid mixture containing 0.80 % C and is formed at 723°C on very slow cooling.
It is a very fine platelike or lamellar mixture of ferrite and cementite.
The white ferritic background or matrix contains thin plates of cementite (dark).

10. Definition of structures
Pearlite
Average properties are:
Tensile strength = 120,000 psi;
Elongation = 20 % in 2 in.;
Hardness = Rockwell C 20, Rock­well B , or BHN

11. Definition of structures
Austenite is an interstitial solid solution of Carbon dissolved in  (F.C.C.) iron.
Maximum solubility is 2.0 % C at 1130°C.
High formability, most of heat treatments begin with this single phase.
It is normally not stable at room temperature. But, under certain conditions it is possible to obtain austenite at room temperature.

12. Definition of structures
Austenite
Average properties are:
Tensile strength = 150,000 psi;
Elongation = 10 percent in 2 in.;
Hardness = Rockwell C 40, approx; and
toughness = high

13. Definition of structures
Cementite or iron carbide, is very hard, brittle intermetallic compound of iron & carbon, as Fe3C, contains 6.67 % C.
It is the hardest structure that appears on the diagram, exact melting point unknown.
Its crystal structure is orthorhombic.
It is has
low tensile strength (approx. 5,000 psi), but
high compressive strength.

14. Definition of structures
Ledeburite is the eutectic mixture of austenite and cementite.
It contains 4.3 percent C and is formed at 1130°C.

15. Definition of structures
Martensite - a super-saturated solid solution of carbon in ferrite.
It is formed when steel is cooled so rapidly that the change from austenite to pearlite is suppressed.
The interstitial carbon atoms distort the BCC ferrite into a BC-tetragonal structure (BCT).; responsible for the hardness of quenched steel

16. The Iron-Iron Carbon Diagram
A map of the temperature at which different phase changes occur on very slow heating and cooling in relation to Carbon, is called Iron- Carbon Diagram.
Iron- Carbon diagram shows
the type of alloys formed under very slow cooling,
proper heat-treatment temperature and
how the properties of steels and cast irons can be radically changed by heat-treatment.

17. Various Features of Fe-C diagram
Phases present L
a ferrite
BCC structure
Ferromagnetic
Fairly ductile d
BCC structure
Paramagnetic
g austenite
FCC structure
Non-magnetic
ductile
Fe3C cementite
Orthorhombic
Hard
brittle
Reactions
Peritectic L + d = g
Max. solubility of C in ferrite=0.022%
Max. solubility of C in austenite=2.11%
Eutectic L = g + Fe3C
Eutectoid g = a + Fe3C

18. Three Phase Reactions
Peritectic, at 1490 deg.C, with low wt% C alloys (almost no engineering importance).
Eutectic, at 1130 deg.C, with 4.3wt% C, alloys called cast irons.
Eutectoid, at 723 deg.C with eutectoid composition of 0.8wt% C, two-phase mixture (ferrite & cementite). They are steels.

19. How to read the Fe-C phase diagram
Eutectic
eutectoid
Pearlite and Cementine
Austenite
Ferrite
Pearlite
Pearlite and
Carbide
Steel
Cast iron

20. The Iron-Iron Carbide Diagram
The diagram shows three horizontal lines which indicate isothermal reactions (on cooling / heating):
First horizontal line is at 1490°C, where peritectic reaction takes place:
Liquid +  ↔ austenite
Second horizontal line is at 1130°C, where eutectic reaction takes place:
liquid ↔ austenite + cementite
Third horizontal line is at 723°C, where eutectoid reaction takes place:
austenite ↔ pearlite (mixture of ferrite & cementite)

21. Delta region of Fe-Fe carbide diagram
Liquid +  ↔ austenite

22. Ferrite region of Fe-Fe Carbide diagram

23. The Austenite to ferrite / cementite transformation in relation to Fe-C diagram

24. The Austenite to ferrite / cementite transformation in relation to Fe-C diagram
In order to understand the transformation processes, consider a steel of the eutectoid composition. 0.8% carbon, being slow cooled along line x-x‘.
At the upper temperatures, only austenite is present, with the 0.8% carbon being dissolved in solid solution within the FCC. When the steel cools through 723°C, several changes occur simultaneously.

25. The Austenite to ferrite / cementite transformation in relation to Fe-C diagram
The iron wants to change crystal structure from the FCC austenite to the BCC ferrite, but the ferrite can only contain 0.02% carbon in solid solution.
The excess carbon is rejected and forms the carbon-rich intermetallic known as cementite.

26. Bibliography MSM by O.P Khanna www.slideshare.net www.studynotes.ie
Steel.keytometals.com

27. Thanks